Syngas is a mixture of hydrogen and carbon monoxide and it is produced by conversion of methane and other hydrocarbons with steam over a steam reforming catalyst through the steam methane reforming process in one form or another. In ammonia production tubular reforming is combined with secondary reforming and air is added to the secondary reformer to combust residual methane from the primary reformer and to adjust the syngas ratio to achieve the H2/N2 ratio of approx. 3.0 for the ammonia synthesis. When N2 is an undesired constituent in syngas, pure oxygen can be used as oxidant in the secondary reformer and this is the case in methanol plants. For methanol production a so-called “two-step reforming”-concept combining a tubular reformer with an oxygen-blown secondary reformer in the syngas section. The process lay-out includes adiabatic pre-reforming, tubular reforming and oxygen-blown secondary reforming. The oxygen acts as a source for internal process combustion of hydrocarbons coming from the tubular reformer. Operating conditions of the oxygen-blown secondary reformer are characterized by higher combustion temperatures than in air-fired lay-outs.
Another syngas technology is Autothermal reforming (ATR) which is a stand-alone process technology in which the tubular reformer is eliminated from the lay-out and pre-reformed natural gas is sent directly to an ATR reformer in which hydrocarbons are combusted by oxygen. By omitting the tubular reformer, the steam addition to the feed-streams can be reduced significantly.
For large-scale methanol plants, Autothermal reforming is today an alternative to two-step reforming technology for larger production capacity methanol plants of ie 5000 tpd.
ATR is a preferred technology for syngas manufacturing in GTL plants (Gas-to-Liquid) in which diesel is produced via Fischer-Tropsch (FT) synthesis. Syngas with H2/CO ratio of 2.0 can be produced directly with ATR reforming and such is especially suited for FT synthesis and production of FT liquids.
Operating conditions for the ATR reformer are even more severe than for oxygen blown secondary reformers and even more robust reactor layout are required for operation in ATR reformers. The steam-to-carbon feed ratio is lower and the combustion intensity and the flame temperature are much higher in ATR reformers.
The reactor design for ATR, oxygen-blown secondary reformers and air-blown secondary reformers comprises a burner, a combustion chamber, target tiles, a fixed catalyst bed, a catalyst bed support structure, a refractory lining, and a reactor pressure shell.
The catalyst bed support system serves both as structural support for the catalyst bed and as an outlet flow distributor guiding the syngas from the catalyst bed into the transfer line to the waste heat recovery system downstream the reformer. Such catalyst support systems have lay-outs that can be of various geometry, i.e. cone type structures, arch-type or dome type constructions. Dome and arch shaped catalyst support systems can suffer from failure and collapse. Cone type of catalyst support system has been used with good performance as catalyst support system, and failures and collapses with this type have not been observed. However, some degree of maintenance is generally reported to individual pieces of the ceramic elements and especially thin walled structural elements in vertical and/or horizontal direction.
The catalyst support system may be in contact with inerts for instance in the shape of spheres or lumps. These deliver forces onto the catalyst support system in points where stress levels can become excessive and initiate cracks which may result in failing of the bricks which the catalyst support system is made of.
Also the inerts block or partly block the flow area in the catalyst support system in the flow channels or in the inlet section of the channels, making the pressure drop over the support rise.
Known art offers little solution to this problem, as can be seen in the following references, where:
US2002071790 describes an integrated reactor for producing fuel gas for a fuel cell, the integrated reactor comprises a waste gas oxidizer (WGO) assembly having an associated WGO chamber, an inlet, an outlet and a flow path for exothermic gases produced in the WGO chamber. The integrated reactor has an auto-thermal reactor (ATR) assembly located within the WGO chamber. The ATR assembly has an inlet means and an outlet means for process gases flowing there through and a catalyst bed which is intermediate the inlet and outlet means. At least a part of the inlet means of the ATR assembly is located in the flow path of the WGO chamber to facilitate the transfer of thermal energy.
CN202606129 describes a non-metal high-temperature catalyst supporting piece. The catalyst supporting piece is arranged in a reactor and comprises a corundum brick support and a foamed ceramic plate arranged on the corundum brick support; and mounting contact surfaces of the corundum brick support and the foamed ceramic plate are saw-toothed; the corundum brick support is formed by integrally mortising at least two kinds of specially-shaped corundum bricks; mortar is filled in gaps among the specially-shaped corundum bricks; and ceramic fibre paper is filled in an annular gap between the corundum brick support and the inner wall of the reactor. The catalyst supporting piece has the characteristics of high temperature resistance, corrosion resistance, high mechanical strength, convenience in mounting, long service life and no catalyst leakage. The foamed ceramic plates of different specifications can selected according to the granular size of catalysts, and the tops of the corundum bricks contacted with the foamed ceramic plates have tooth-shaped structures, so that the smoothness of airflow is guaranteed; mortise structures are adopted by the corundum bricks, and the mortar is filled in the gaps among the corundum bricks, so that long-period running of equipment can be guaranteed; and the catalyst supporting piece is widely applied to chemical industry, pharmaceutical industry, petrochemical industry and the like.
None of the above known art references offer a solution to the problem of protecting a catalyst support system in a chemical reactor against damage and blockage by catalyst or other reactor particles.